Microswitch

ABSTRACT

A microswitch employing a movable contact actuating spring made of a single resilient metal plate so as to comprise a contact spring section having the movable contact and an operating spring section branched from the contact spring section. The contact spring section is resiliently hinged between a common terminal metal fitting and an insulative support member so as to be substantially in an S-shape and to have the movable contact engaged with a normally closed fixed contact, and the operating spring section engages at a free end with a push button. Actuation of the button causes the actuating spring to be snapped over to its position in which the movable contact engages a normally opened fixed contact and releasing of the button causes the spring to return to its original position.

United States Patent [191 Nishio et al.

[ Dec. 24, 1974 MICROSWITCH [75] Inventors: Minoru Nishio, Neyagawa; Norio Sagawa, Osaka, both of Japan [73] Assignee: Matsushita Electric Works, Ltd.,

Osaka, Japan [22] Filed: Sept. 12, 1973 [21] Appl. No.: 396,487

[30] Foreign Application Priority Data Sept. 14, 1972 Japan 47-107490 52 us. C1. .L 200/67 DB [51] Int. Cl. H01h 13/36 [58] Field of Search 200/67 DB, 67 DA;

[56] References Cited UNITED STATES PATENTS 1,215,665 2/1917 Landis 200/67 DB.

1,719,096 7/1929 Burke 200/67 DB 2,133,309 10/1938 Schmidingeruf. 200/67 DB 2,167,543 7/1939 Bugenhagen 200/67 DB 2,395,698 2/1946 Tiffany 200/67 DB Jacobs, Jr. 200/67 DA Primary ExaminerDavid Smith, Jr. Attorney, Agent, or Firm-Wolfe, Hubbard, Leydig, Voit & Osann, Ltd.

ABSTRACT A microswitch employing a movable contact actuating spring made of a single resilient metal plate so as to comprise a contact spring section having the movable contact and an operating spring section branched from the contact spring section. The contact spring section is resiliently hinged between a common terminal metal fitting and an insulative support member so as to be substantially in an S-shape and to have the movable contact engaged with a normally closed fixed contact, and the operating spring section engages at a free end with a push button. Actuation of the button causes the actuating spring to be snapped over to its position in which the movable contact engages a normally opened fixed contact and releasing of the button causes the spring to return to its original position.

9 Claims, 10 Drawing Figures PATENTED M 3. 857. 003

sum 1 OF 4 PATENTEBHE Z I I 3;857. 003

sum 3 OF 4 Fig. 5

MICROSWITCH This invention relates to a microswitch including an S-shaped actuating spring and, more particularly, to a microswitch having a high contact pressure and operatable under a light load.

Conventional microswitches of this kind include such component elements of a spring system of a switch mechanism as an actuating lever, movable contact maker and turning spring respectively as independent members. Therefore, they are high in the number of component parts, complicated in the assembling work and high in the cost.

Further, in order to realize a microswitch light in the operation while obtaining a high pressure, a further correcting spring must be added in the push button operating direction and thus the cost is higher.

Further, in the conventional microswitch including the S-shaped actuating spring, a large force is required to operate the switch, no sufficient contact pressure is obtained, the turning position of the movable contact is unstable and, further, the contacting stability of the contacts is hard to obtain.

The present invention is suggested to eliminate the above mentioned defects.

A main object of the present invention is to provide a microswitch wherein a spring system of snap action switch can be completed by using a single actuating spring.

Another object of the present invention is to provide a microswitch which is capable of operating under a light load.

A further object of the present invention is to provide a microswitch wherein a relatively high contact pressure is obtained in spite of a light load.

Another object of the present invention is to provide a microswitch wherein the push button operating stroke is large.

A further object of the present invention is to provide a microswitch wherein wiping and rolling actions are given to the movable contact so that the contact action will be stable and the contacts will be prevented from sticking to one another. 7

Yet another object of the present invention is to provide a microswitch wherein the turning position of the movable contact is stable.

A yet further object of the present invention is to provide a microswitch which is easy to assemble.

Now the present invention shall be explained with reference to certain preferred embodiments shown in the accompanying drawings, in which:

FIG. 1 is a perspective view of a microswitch according to the present invention;

FIG. 2 is a vertically sectioned view of the switch shown in FIG. 1;

FIG. 3 is a partly sectioned view with the lid, plate spring and push button removed in FIG. 2;

FIG. 4 is a perspective view showing an embodiment of an actuating spring used in the microswitch according to the present invention;

FIG. 5 is a perspective view of a spring supporting metal fitting and fixed contact member;

FIG. 6 and 7 are perspective views showing other embodiments of the actuating spring;

FIG. 8 is a schematic view showing an example of conventional switches of the type referred to:

FIG. 9 is a force line view showing a balance of forces in the spring system of the microswitch of the present invention; and

FIG. 10 is a diagram for the sake of comparison with FIG. 9.

In conventional microswitches using the S-shaped actuating spring, for example, as shown in FIG. 8, a movable contact 31 is secured to an actuating spring 30 substantially at an intermediate position thereof and the actuating spring'30 is operated directly by a push button 32.

In such microswitch, as the actuating spring is deflected directly by the push button, a large force is required to operate the switch and, in order to obtain a switch of a light load, the contact pressure must be sacrificed.

Further, as the actuating spring is operated directly by the push button, there is no capability of increasing the push button operating stroke as required.

Further, what is most serious in such conventional switch is that, as a problem inherent to the S-shaped spring, its turning position is so unstable that it has been difficult to obtain a microswitch having any desired characteristics.

In FIG. 1 showing in a perspective view'a microswitch according to the present invention, a lid 1 is fixed as fitted to a base 2 provided with terminal metal fittings 3, 4 and 5. The terminal metal fitting 3 is of a common terminal type, 4 is of a normally opened terminal and 5 is of a normally closed terminal. 6 is a push button slidably fitted in a'hole made in the lid 1 so that the push button will be pushed to switch the contacts ON and OFF.

FIG. 2 is a vertically sectioned view of a microswitch of the present invention. FIG. 3 is a sectioned view with the lid 1, push button 6 and actuating plate spring 14 removed from the switch shown in FIG. 2.

. In FIGS. 2 and 3, the terminal metal fitting 3 is extended upright into the lid 1 through the base 2 and has an L-shaped supporting metal member 7 shown in FIG. 5 as secured at the inner end part. This supporting metal member 7 is provided with a slot 8 to engage thereto an end of the actuating plate spring 14. Further, an L-shaped contact member 9 is fitted to an end of the terminal metal fitting 4 similarly extended into the lid 1, and the contact member 9 is provided at the inner end with a fixed contact 10. Further, an L-shaped contact member 11 is secured to a similarly extended end of the terminal metal fitting 5 into the lid 1, and this contact member 11 is provided with a fixed contact 12. The both contacts 10 and'l2 are so arranged as to be above and below and oppose each other. 13 is an engaging section for bearing the other end of the actuating plate spring 1 and molded integrally with the base 2 with an electrically insulative material.

As will be evident from FIG. 2, the actuating plate spring 14 supports a movable contact 22 substantially on the right-hand side in the drawing of its intermediate point, and is branched at a point W located further rightward from the contact 22 so as to form an operat ing spring section 15 and contact spring section 16. Said contact spring section 16 is bent slightly downward preliminarily before the mounting at a bending part 16a which is close to and a little leftward side of the movable contact 22. Further, as seen best in FIG. 4, the contact section 16 is provided at left-hand end in the drawing with an engaging section 17 for engaging with the slot 8 in the supporting member 7 and a projection 18 and at the other end with an engaging section 19 for engaging with the bearing member 13 and a projection 20. 23 is a raised portion in the longitudinal direction made in the operating spring section 15. The actuating plate spring 14 is spported as hinged in position in such that the engaging section 17 will engage in the slot 8 in the supporting member 7 and the other engaging section 19 will engage with the bearing member 13. At this time, since the distance between the both hinging points'of the slot 8 and the bearing member 13 is made relatively smaller than the length of the actuating spring 14 even after being bent at the part 16a, the both side sections of the. bent part 16a of the spring are respectively bent to be curved so that the spring will show substantially an S-shape in its hinged position. The operating spring section 15 abuts resiliently against the lower surface of the push button 6 at a point adjacent its free end.

In the case of the actuating spring 14 as shown in FIG. 4-, the bent part 16a is formed in such that the spring section 16 is once bent upward and then again downward. In either case of FIG. 2 or FIG. 4, the bent part 16a of the actuating spring 14 according to the present invention-is made for the purpose of providing, in the mounted position of the spring 14 as bent in an S-shape, two separate sections which are curved in opposite directions respectively as definitely separated by the bent part 16a as a boundary. With the bent part 16a provided as above, such unique operation and effect as referred to in the following are obtained.

The operation of the microswitch according to the present invention shall be explained in the following. FIG. 1 shows the state in which the contact 22 of the actuating spring 14 is in contact with the fixed contact 12. The force relation in such case is as follows (See FIG. 9):

The balance of forces in the direction x is T'cos T"cos 0 O The balance of forces in the direction yis -(T'sin 0 T"sin 0 R 0 I the spring 14.

With the microswitch of the present invention, as the actuating spring 14 to be used hassuch unique action as described above, the following effects will be obtained. That is:

a. As the bending part 16a is provided substantially in the middle of the actuating spring 14, this part 16a the balancing point of the forces of T'sin 6 and Tsin 0 will become unstable and the quality will become unstable.

b. In the actuating spring of the present invention, the operating spring section 15 is branched further on the right from the movable contact fixing position and bears the push button 6 at the free end, so that the operating stroke will be taken to be longer and more freely than in the case of directly pressing the contact.

spring section 16 with the push button and further, by the principle of the leverage, the switch can be operated by a light force. Therefore, a microswitch of a light load and high contact pressure can be realized.

0. As the actuating spring of the present invention is branched so that the operating spring section 15 will be parallel with the contact spring section 16, a twisting force will be able tobe added to the contact spring section 16 during the push button operation, so that wiping and rolling actions will be given to the contacts and, therefore, the contacting performance will be stable and any possible sticking of the contacts due to fusion between them will be prevented from occurring.

(1. According to the present invention, the spring system of the switch mechanism of microswitches referred to having all the effects in the above paragraphs (a) (c) is made possible by usingonly a single actuating spring so that the number of the component parts can be reduced and the assembling operation can be made easy. v

e. Further according to the present invention, as the terminal metal fittings 3, 4 and 5 are held integrally with the insulating base 2, the terminal mechanism can be handled as one block and the assembling work as of a switch can be made easy. Further, there is no fluctuation in the terminalmechanism.

FIG. 6A shows another embodiment of the actuating spring to be used in the present invention. The actuating spring 14 in this embodiment is branched into an upper leg 25 andlower leg 26 from the vicinity of the contact-22 so as to be substantially Y-shaped. In the ilv lustrated case, the lower leg 26 is made larger than the upper leg 25 which is secured to the lower leg 26. However, it is also possible to make the upper leg 25 larger than the lower leg 26 In assembling this actuating spring 14, the upper leg 25 is brought into abutment against the push button 6 and the lower leg 26 is bent, as shown in FIG. 68, so that the spring will be hinged between the supporting member 7 and bearing member 13 (See FIG. 2).

FIG. 7 shows another embodiment of the actuating spring in the present invention, in which a pair of legs 15 and 16 are formed by punching the spring 14 comprising a single plate so that the respective legs will extend upward and each in the direction of each end of the plate from the intermediate part thereof. The contact 22 is secured to the free end of one leg 16 of the pair of legs, and the other leg 15 is butted tothe push button 6.

will act as a fulcrum and, as different from any conven- 1 tional one, the balancing point of the forces of T'sin 0, and T"sin 6 will be stabilized and a qualitative stability will be obtained. In comparison, if the actuating spring is used without being provided with the preliminary bent part 16a but as bent in the S-shape, as in FIG. 10,

It will be seen that in the various embodiments of the present invention there is a housingwhich defines a central chamber. In such central chamber there is a leaf spring 14 having spade-like ends seated in grooves formed at the respective ends of the chamber. The spring has an unstressed length which is greater than the groove-to-groove dimension so that the spring is stressed in shallow S configuration incident to installing it in the grooves. Thespring, acting between the grooves, has a deadcenter position but is movable overcenter from such deadcenter position. An electrical contact 22 is located along the length of the spring. This contact cooperates with opposed stops 10, 12 which are in the form of contacts. Electrical connection is provided at a groove at-at least one end of the spring. In the preferred embodiment of the invention the stops are so located and the spring is so stressed as to tend to return to one of its overcenter positions. Secured to the body of the spring is a cantilever element 15. Means in the form of a push button are provided for applying lateral force to the remote end portion of the cantilever element for urging the spring temporarily into its opposite overcenter position as long as the push button is depressed. Stated in slightly different terms, the effect of the cantilever, and the force exerted on the cantilever, is to shift the nominal deadcenter position of the spring with respect to the stops, so that when the spring is depressed by the push button the spring tends to seek one of the stops and so that when the push button is released, the spring tends to seek the opposite stop. The cantilever element is sufficiently long, in addition, to provide leverage so that the force required to operate the push button is decreased, while the operating stroke is increased.

While the structure shown in the drawings and described above will be clear from the foregoing, it will be helpful to summarize some of the features and advantages. Thus turning to the preferred form of the invention which is shown in FlG. 2 and diagrammed in FIG. 9, the leaf spring is permanently creased or bent, as indicated at 16a, with the bend extending transversely of the spring in a position near the center of the spring and adjacent the spring contact. This causes the second or left-hand end portion 16, prior to installation, to occupy a plane which differs from the plane of the first or right-hand end portion. Specificially, the plane of the secone end portion 16 is at an angle with respect to the first end portion, the portion 16 being bent downwardly away from the pushbutton.

As stated, the bend 16a provides a well defined line of demarcation between the first and second end portions of the spring which are, as illustrated in FIG. 2, bowed in opposite directions.

Secondly, by reason of the bend 16a the reaction forces exerted by the grooves against the ends of the spring, and which are indicated at T and T", both have components extending in the direction of the pushbutton, that is, upwardly. This is to be contrasted with use of a spring without a permanent bend, as diagrammed in FIG. 10, which is deformed into S configuration incident to installation but which has no well defined junction between oppositely bowed portions and in which the vertical components of the reaction forces (T' and T") are directed in opposite directions, one upwardly and one downwardly. It is found that a microswitch leaf spring which includes the bend 16a, with the vertical components of reaction forces T and T" both directed in the same direction, that is, upwardly, provides a more stable, that is, predictable, switch operating point when the pushbutton is pressed.

In an alternate version of the invention illustrated in FIG. 4, a bend 16a is also provided at the center of the spring. but instead of being a single bend is a double bend so that the first and second (right and left-hand) portions prior to installation lie in planes which are spaced from one another. in this version, as in the earlier version, the bent portion 16a provides a well defined region of demarcation between the two end portions of the spring when such end portions are bowed in opposite directions.

The cantilever element, indicated at 15 (see, for example, FIG. 4), is integrally joined to the leaf spring in the region 19 so that the leaf spring and cantilever both may be conveniently stamped out of a single sheet of springy metal, with the cantilever portion preferably being rigidified by the longitudinally extending embossment 23.

We claim:

1. In a microswitch the combination comprising a case, a push button slidably fitted to said case, an actuating plate spring to be pushed by said push button, a supporting member engaging with an end of said actuating plate spring, said supporting member being fixed to a common terminal metal fitting, a pair of fixed contacts opposed to a movable contact provided on said actuating plate spring, said fixed contacts being fixed respectively to a terminal metal fitting through a supporting member, a bearing section engaging with the other end of said actuating plate spring and an insulating base supporting said terminal metal fittings, wherein said actuating plate spring has a pair of legs formed by punching so as toextend respectively toward each end substantially from intermediate part of the spring, one of said legs has a movable contact near the base and the free end of the other leg is opposed to the push button.

2. A microswitch including a housing defining a central chamber and mounting a slideable push button, means defining opposed and alined grooves at the respective ends of the chamber, a leaf spring having first and second end portions seated spade-like in the respective grooves and having a normal unstressed length greater than the groove-to-groove dimension so that the spring is stressed upon installation into a shallow S configuration, the spring having a deadcenter position and having a contact adjacent the center of the spring, opposed stops in the, housing located at the spring contact on opposite sides of the deadcenter position for defining a normal position of the spring on one side of deadcenter and an alternate position on the other side of deadcenter, means at at least one of the grooves and at at least one of the stops for providing electrical switch connections, the spring having an integral arm extending along the edge of the spring and integralwith the first end portion to form a cantilever-element, the tip of the cantilever element being arranged in the path of movement of the push button for applying lateral pressure to the spring for urging the spring over deadcenter into its alternate position, the spring having a permanent bend transversely in the region of the center thereof so that prior to installation the first and second end portions of the spring lie in different planes.

3. A microswitch including a housing defining a central chamber and mounting a slideable push button, means defining opposed and alined grooves at the respective ends of the chamber, a leaf spring having first and second end portions seated spadelike in the respective grooves and having a normal uunstressed length greater than the groove-to groove dimension so that the spring is stressed upon installation into a shallow S configuration, the spring having a deadcenter position and having a contact adjacent the center of the spring, opposed stops in the housing located on opposite sides of the deadcenter position at least one of which cooperates with the spring contact for defining a normal position of the spring on one side of deadcenter and an al ternate position on the other side of deadcenter, means at at least one of the grooves and at at least one of the stops for providing electrical switch connections, and means including a cantilever element having a base anchored to the first end portion of the spring and extending along the spring to a point adjacent the second end portion thereof, the tip of the cantilever element being arranged in the path of movement of the push button for applying lateral pressure to the spring for urging the spring over deadcenter into its alternate position, the spring having a permanent bend transversely in the region of the center thereof so that prior to installation the first and second end portions of the spring lie in different planes. I

4. The combination as claimed in claim 3 in which the spring has a transversely extending permanent bend in the region of the center thereof so that the end portions of the spring lie in different planes which are at an angle to one another, the second end portion of the spring being bent in a direction away from the'push button sothat when the spring is seated in the grooves there is a reaction force having a component in opposition to the push button.

5. The combination as claimed in claim 3 in which the spring has a single transversely extending perma nent bend in the region of the center thereof so that the end portions of the spring lie indifferent planes which are at an angle to one another.

6. The combination as claimed in claim 3 in which the spring is doubly bent in the region of the center in opposite directions so that the end portions of the spring lie in different planes which are spaced from one another. v

7. The combination as claimed in claim 3 in which the contact is adjacent the first end portion of the spring and in which the first end portion of the spring is stiffer than the second end portion.

8. A microswitch including a housing defining a central chamber and mounting a slideable push button, means defining opposed and alined grooves at the respective ends of the chamber, a leaf spring having first and second end portions seated spadelike in the respective grooves andhaving a normal unstressed length greater than the groove-to-groove dimension so that the spring is stressed upon installation into a shallow S configuration, the spring having a deadcenter position and having a contact adjacent the center of the spring, opposed stops in the housing located at the spring contact on opposite sides of the deadcenter position for defining a normal position of the spring on one side of deadcenter and an alternate position on the other side of deadcenter, means at at least one of the grooves and at at least one of the stops for providing electrical switch connections, and means including a cantilever element anchored to the'edge of the first end portion of the spring and extending along the spring toward the second end portion thereof, the tip of the cantilever element being arranged in the path of movement of the push button for applying lateral pressure to the spring for urging the spring over deadcenter into its alternate position, the spring having a permanent bend transversely adjacent the spring contact to separate the spring into two well-defined regions which are bowed in opposite directions thereby to increase the stability of the operating point of the switch as the push button is progressively pressed. l I

9. a microswitch including a housing defining a central chamber and mounting a slideable push button,

means defining opposed and alined grooves atthe respective ends of the chamber, a leaf spring having first and second end portions seated spadelike in the respective grooves and having a normal unstressed length greater than the groove-to-groove dimension so that the spring is stressed upon installationinto a shallow S configuration, the spring having a deadcenter position and having a spring contact, opposed stops in the housing located at. the spring contact on opposite sides of the deadcenter position for defining a normal position of the spring on one side of dead-center and an alternate position on thepther side of deadcenter, means at at least one of the. grooves and at at least one of the stops for providing electrical switch connections, and means including a cantilever element anchored to the edge of the first end portion of the spring and extending along the spring toward the second end portion thereof, the tip of the cantilever element being arranged in the path of movement of the pushbutton for applying lateral pressure to the spring for urging the spring over dead-center into its alternate position, the spring having a permanent bend transversely in the general region of the center thereof so that prior to installation the first and second end portions of the spring lie in differ.- ent planes, bearing an angle to'one another, with the second end portion being bent in a direction away from the push button so that when the spring is installed in the grooves both end portions are subject to respective vertical components of reaction force at the grooves in a direction toward the'push button, the spring contact being positioned between the bend in the spring and the region of anchoring of the cantilever element. 

1. In a microswitch the combination comprising a case, a push button slidably fitted to said case, an actuating plate spring to be pushed by said push button, a supporting member engaging with an end of said actuating plate spring, said supporting member being fixed to a common terminal metal fitting, a pair of fixed contacts opposed to a movable contact provided on said actuating plate spring, said fixed contacts being fixed respectively to a terminal metal fitting through a supporting member, a bearing section engaging with the other end of said actuating plate spring and an insulating base supporting said terminal metal fittings, wherein said actuating plate spring has a pair of legs formed by punching so as to extend respectively toward each end substantially from intermediate part of the spring, one of said legs has a movable contact near the base and the free end of the other leg is opposed to the push button.
 2. A microswitch including a housing defining a central chamber and mounting a slideable push button, means defining opposed and alined grooves at the respeCtive ends of the chamber, a leaf spring having first and second end portions seated spade-like in the respective grooves and having a normal unstressed length greater than the groove-to-groove dimension so that the spring is stressed upon installation into a shallow S configuration, the spring having a deadcenter position and having a contact adjacent the center of the spring, opposed stops in the housing located at the spring contact on opposite sides of the deadcenter position for defining a normal position of the spring on one side of deadcenter and an alternate position on the other side of deadcenter, means at at least one of the grooves and at at least one of the stops for providing electrical switch connections, the spring having an integral arm extending along the edge of the spring and integral with the first end portion to form a cantilever element, the tip of the cantilever element being arranged in the path of movement of the push button for applying lateral pressure to the spring for urging the spring over dead-center into its alternate position, the spring having a permanent bend transversely in the region of the center thereof so that prior to installation the first and second end portions of the spring lie in different planes.
 3. A microswitch including a housing defining a central chamber and mounting a slideable push button, means defining opposed and alined grooves at the respective ends of the chamber, a leaf spring having first and second end portions seated spadelike in the respective grooves and having a normal uunstressed length greater than the groove-to groove dimension so that the spring is stressed upon installation into a shallow S configuration, the spring having a deadcenter position and having a contact adjacent the center of the spring, opposed stops in the housing located on opposite sides of the deadcenter position at least one of which cooperates with the spring contact for defining a normal position of the spring on one side of deadcenter and an alternate position on the other side of deadcenter, means at at least one of the grooves and at at least one of the stops for providing electrical switch connections, and means including a cantilever element having a base anchored to the first end portion of the spring and extending along the spring to a point adjacent the second end portion thereof, the tip of the cantilever element being arranged in the path of movement of the push button for applying lateral pressure to the spring for urging the spring over deadcenter into its alternate position, the spring having a permanent bend transversely in the region of the center thereof so that prior to installation the first and second end portions of the spring lie in different planes.
 4. The combination as claimed in claim 3 in which the spring has a transversely extending permanent bend in the region of the center thereof so that the end portions of the spring lie in different planes which are at an angle to one another, the second end portion of the spring being bent in a direction away from the push button so that when the spring is seated in the grooves there is a reaction force having a component in opposition to the push button.
 5. The combination as claimed in claim 3 in which the spring has a single transversely extending permanent bend in the region of the center thereof so that the end portions of the spring lie in different planes which are at an angle to one another.
 6. The combination as claimed in claim 3 in which the spring is doubly bent in the region of the center in opposite directions so that the end portions of the spring lie in different planes which are spaced from one another.
 7. The combination as claimed in claim 3 in which the contact is adjacent the first end portion of the spring and in which the first end portion of the spring is stiffer than the second end portion.
 8. A microswitch including a housing defining a central chamber and mounting a slideable push button, means defining opposed and alined groovEs at the respective ends of the chamber, a leaf spring having first and second end portions seated spadelike in the respective grooves and having a normal unstressed length greater than the groove-to-groove dimension so that the spring is stressed upon installation into a shallow S configuration, the spring having a deadcenter position and having a contact adjacent the center of the spring, opposed stops in the housing located at the spring contact on opposite sides of the deadcenter position for defining a normal position of the spring on one side of deadcenter and an alternate position on the other side of deadcenter, means at at least one of the grooves and at at least one of the stops for providing electrical switch connections, and means including a cantilever element anchored to the edge of the first end portion of the spring and extending along the spring toward the second end portion thereof, the tip of the cantilever element being arranged in the path of movement of the push button for applying lateral pressure to the spring for urging the spring over deadcenter into its alternate position, the spring having a permanent bend transversely adjacent the spring contact to separate the spring into two well-defined regions which are bowed in opposite directions thereby to increase the stability of the operating point of the switch as the push button is progressively pressed.
 9. a microswitch including a housing defining a central chamber and mounting a slideable push button, means defining opposed and alined grooves at the respective ends of the chamber, a leaf spring having first and second end portions seated spadelike in the respective grooves and having a normal unstressed length greater than the groove-to-groove dimension so that the spring is stressed upon installation into a shallow S configuration, the spring having a deadcenter position and having a spring contact, opposed stops in the housing located at the spring contact on opposite sides of the deadcenter position for defining a normal position of the spring on one side of dead-center and an alternate position on the other side of deadcenter, means at at least one of the grooves and at at least one of the stops for providing electrical switch connections, and means including a cantilever element anchored to the edge of the first end portion of the spring and extending along the spring toward the second end portion thereof, the tip of the cantilever element being arranged in the path of movement of the pushbutton for applying lateral pressure to the spring for urging the spring over dead-center into its alternate position, the spring having a permanent bend transversely in the general region of the center thereof so that prior to installation the first and second end portions of the spring lie in different planes, bearing an angle to one another, with the second end portion being bent in a direction away from the push button so that when the spring is installed in the grooves both end portions are subject to respective vertical components of reaction force at the grooves in a direction toward the push button, the spring contact being positioned between the bend in the spring and the region of anchoring of the cantilever element. 